On the genus Artyfechinostomum (Lane, 1915) (Echinostomatidae: Trematoda)

Artyfechinostomum Lane, 1915 (type A. sufrartyfex Lane, 1915) is a synonym of Paryphostomum Dietz, 1909 (type P. radiatum Dujardin, 1845). While the general morphology of the two forms is similar and places them both in the family Echinostomatidae, other characters clearly place them in different genera of this family. In Artyfechinostomum the cirrus-sac extends far posterior to the acetabulum, and the right and left fields of vitellaria in the post-testicular region are confluent. In Paryphostomum the cirrus-sac is small and anterior to the middle of the acetabulum and the vitellaria in the post-testicular region are not confluent. These differences entitle Artyfechinostomum to be placed in a separate genus. The species Paryphostomum indicum Bhalerao, 1931 and P. mehrai Jain, 1957 are transferred to the genus Artyfechinostomum.

The attachment of the monogenean Discocotyle sagittata Leuckart to the gills of Salmo trutta L

The monogenetic trematodeDiscocotyle sagittataattaches itself to the gills ofSalmo truttawith its long axis inclined to the long axis of the primary lamella to which it is attached, the direction of inclination being determined by the incidence of the gill-ventilating current of the host. The inclination is to some extent brought about by an asymmetrical disposition of the posterior adhesive organs, butDiscocotyleappears to retain a primitive unspecialized character in that the asymmetrical disposition is facultative and not obligatory and permanent as inAxine.

The adhesive apparatus consists of four pairs of clamps and one pair of hooks. The hooks appear to be the persistent posterior hooks of the larva.

Each clamp is operated by an extrinsic muscle-tendon-fair-lead-hinged-jaws system generally similar but possibly less efficient than the corresponding system inPlectanocotyle gurnardi.Scheuring's and Sproston's interpretations of the clamp-closing mechanism ofDiscocotyleas a spring system are wrong.

Studies on larval trematodes infecting freshwater snails in London (U.K.) and some adjoining areas. II. Gymnocephalous cercariae

Two new species of Gymnocephalous cercariae are described from London. Cercariae lophocerca Fil. is recorded for the first time from Britain. A description of this cercaria is given.

Further observations on Artyfechinostomum mehrai (Faruqui) (Echinostomatidae: Trematoda)

While working on the life cycle of Cercaria mehrai Faruqui, 1930, the author obtained the adults from the intestine of experimentally infected white rats. The trematodes thus obtained were reported as belonging to the genus Paryphostomum Dietz, 1909. In view of the facts that the collar spines are 43 in number, the vitellaria are confluent in the post-testicular region and the cirrus-sac extends far behind the acetabulum, P. mehrai is transferred to the genus Artyfechinostomum Lane, 1915, which is, in author's opinion, a valid genus (Jain, 1959).

The larval trematodes of certain fresh-water molluscs. I. The furcocercariae

(1) Eight species of furcocercous cercariae have been found during a 3-year study of the trematode larvae harboured by certain fresh-water molluscs in Glamorganshire. Of these four are new species, two have previously been reported from South Wales by Rees (1932) and the remaining two species have been recorded in Europe but not in Britain.

(2) Detailed descriptions are given of the four new species and the last two species which had not been completely described hitherto. The life cycles, as far as are known, of all the the species are outlined; the mollusc hosts are listed and for each cercaria a comparison with related species is given.

(3) C. hamburgensis Komiya has been proved experimentally to be the larva of Apatemon gracilis minor Yam. and according to the law of priority becomes C. a.g. minor.

Preliminary note on the anatomy of a polystome from the bladder of Xenopus laevis Daud

Six specimens of Xenopus laevis obtained from University College, London, were examined for polystomes; one harboured an adult worm measuring 2·1 mm. in length and two immature specimens, both 0·8 mm. in length, and one was parasitized by a single mature specimen measuring 2·4 mm. in length.

On a new trematode, Astiotrema sudanensis, sp. nov., from a freshwater turtle in the Sudan

Seven specimens of this new species were collected from the intestine of a freshwater turtle, Trionyx triungnis (═T. nilotica) in the Sudan.

These are lanceolate worms which gradually taper to rounded ends, with a length of 2⋅5–2⋅9 mm. and a width of 0⋅6–0⋅9 mm. The cuticle is invested with scales, dense in the anterior half of the worm, but becoming more and more sparse towards the caudal end. The oral sucker is large, measuring 0⋅23–0⋅27 mm. in diameter and is about one and a half times the diameter of the ventral sucker which measures 0⋅14–0⋅17 mm. in diameter. Both suckers lie in the anterior half of the body. The mouth is subterminal and leads to a pharynx which is stout, 0⋅7–0⋅8 mm. by 0⋅11–0⋅12 mm., and leads to a long oesophagus of 0⋅25–0⋅32 mm. in length. The caeca terminate at the posterior border of the posterior testis or slightly anterior to it.

Studies on larval trematodes infecting freshwater snails in London (U.K.) and some adjoining areas. III. "Lophocercous" cercariae

Representatives of the ‘Lophocercous’ group are recorded from Britain for the first time. Two new species are described and a summary of the classification of this group is discussed.

Paramphistomum phillerouxi sp. nov. Paramphistomatidae) and its development in Bulinus forskalii

(1)Paramphistomum phillerouxi sp.nov. from rumina of cattle in Northern Rhodesia is described and its morphology compared with that of Paramphistomum microbothrium Fischoeder from Egypt, Kenya, Northern Rhodesia, and South Africa.

(2)Bulinus forskalii (Ehrenberg) is a natural intermediate host of P. phillerouxi in Northern Rhodesia and Tanganyika. Of other snails, Bulinus senegalensis (Muller) from Gambia was successfully infected experimentally, and Bulinus cernicus (Morelet) in Mauritius was found naturally infected with P. phillerouxi.

(3) The development of P. phillerouxi in Bitlinus forskalii is described. The sporocyst gives birth to 18 to 28 rediae. These firstgeneration rediae are able to produce daughter rediae as well as cercariae. It seemed that not all of the first-generation rediae started to produce daughter rediae first. Some of the rediae began by producing cercariae and produced a few daughter rediae later alongside numerous cercariae. There is some evidence that the subsequent generations of rediae are also capable of developing daughter rediae and cercariae simultaneously.

(4) The first young cercariae to leave the parent rediae were observed 21 days after exposure of the snails to a single miracidium each, and the first shedding of mature cercariae was noted 42 days after the exposure, the snails being kept at 20°C.

Trematodes of fishes from the Red Sea. 10. On three new Cryptogonimidae including two new genera

The three trematode specimens described in this paper were collected by the senior author at the Marine Biological Station, Ghardaga, Red Sea; they are deposited in the collections of the Department of Parasitology, Ein-Shams University, Cairo, U.A.R.

The dimorphism of Polystoma integerrimum (Frolich) Rudolphi and its bearing on relationships within the Polystomatidae. III

A redescription is given of the morphology of the bladder (normal) and branchial (neotenic) forms and the structure'of the larva of Polystoma integerrimum, including a description of the histological changes accompanying digestion, and an account of the peripheral sensory system of the bladder adult.

PARAMPHISTOMUM SUKUMUM SP.NOV. AND OTHER STOMACH-FLUKES FROM CATTLE IN THE SUKUMALAND AREA OF THE LAKE REGION, TANGANYIKA

The morphology of Paramphistomum sukumum sp.nov. from Bos indicus in the Lake Region of Tanganyika, East Africa, is described and illustrated.

A list is given showing the incidence of nine species of the family Paramphistomatidae and three species of the family Gastrothylacidae found in cattle in the Sukumaland area of the Lake Region of Tanganyika.

AN ANALYSIS OF THE MOLLUSCAN HOSTS OF THE TREMATODES OF BIRDS AND MAMMALS AND SOME SPECULATIONS ON HOST-SPECIFICITY

Data on 279 species of trematodes of birds and mammals are analysed in tables, to show the molluscan orders and families that act as first intermediate hosts of various trematode families.

Host-specificity is highly developed in the first larvae of trematodes and it is suggested that, as a consequence of this, certain species, genera and families of molluscs harbour a greater variety of trematodes than others. The families Lymnaeidae, Physidae, Planorbidae, Hydrobiidae and Thiaridae are by far the most important first-intermediate hosts of the trematodes of birds and mammals whose life cycles are known; each family acting as host of not less than twenty-four species and eight families of trematodes.

This paper is published with the approval of the Director General of Health, Canberra, A.C.T.